318 
HICK AND CASH: AFFINITIES OF LEPIDODENDRON. 
of higher groups their vahie is variable, and is notoriously small in 
the case of the group to which the genera we are dealing with 
belong."' In Lepidodendron the want of further knowledge of leaf 
structure is undoubtedly felt, but what we do know points to the 
same conclusions as the structure of the stem, or at least is not 
opposed to them. The fruits are of prime importance in the search for 
affinities, but rather on the ground of their general organization and 
the nature of the reproductive bodies they bear than on the minuter 
details of their structure. This is well seen in the living genus 
Lijcopodium, in which there are species ivitk,d^\\(\. at least one without, 
a distinctly differentiated fruit cone. 
On these gi'ounds we are of opinion that our limited knowledge 
of the fruits-, leaves, and roots of Lepidodp7idron, though much to be 
regretted, and to be remedied at the earliest possible moment, while 
suggesting caution, ought not to deter us from attempting to evaluate 
the facts we have already acquired. 
Lepidodendron. 
In summarising the anatomical and histological characters of the 
genus Lepidodendron we will take the organs in the order usually 
followed by descriptive writers. There is some objection to this, 
inasmuch as it is impossible to keep to one type of 'the genus in all 
cases, while in others the type to which the organ belongs cannot be 
definitely determined. But the advantages of this course appear to 
be much greater than those of any other, and we have therefore 
adopted it. 
I. The Root. 
Most palfeobotanists are agreed that the roots of several Carbo- 
niferous genera must be sought in Stigmaria, seeing that stems of 
Sigillaria, Lepidodendron and Knorria have all been found in organic 
connection therewith. But there is some divergence of opinion as to 
whether Stigmaria itself or its appendages are the true roots. 
Williamsont holds that the axis of Stigmaria " viewed as an organ" 
is a root, and that the appendages are rootlets. Briefly stated, the 
* Sach's Text Book of Botany, 2nd Eng. ed., p. 461. 
t Stigmaria ficoides.'" Palseontographical Society's publication, 1886. 
